1. Field of the Invention
This invention generally relates to a device for measuring the thickness of glass, and, more particularly, a thickness measuring device for insulating glass.
2. Description of the Prior Art
In the window and glass replacement profession, there is often the need to accurately determine the thickness of glass for replacement without an edge of the window being replaced being readily available for measurement. This is particularly critical with windows using insulating glass, i.e., two (or more) sheets of glass separated by air space, wherein the air within the separation acts as a thermal barrier. The difference in thickness between commonly available types of insulating glass may be as little as 1/16-inch, yet that thickness must be accurately determined for ordering and installation of a replacement.
The prior art has developed several devices for measuring the thickness of transparent materials from a single side. Such devices, as in U.S. Pat. Nos. 1,503,543; 1,756,785; 1,875,665; and 3,807,870 commonly utilize an active light source in conjunction with optics to measure the thickness of the material. Such devices are normally expensive and cumbersome, and not designed for field use. Furthermore such devices are not capable of directly measuring the thickness of insulating glass.
U.S. Pat. No. 3,320,849 by J. R. Cumberland presents a glass thickness gauge which is convenient for use, but is not capable of measuring the thickness of insulating glass.
There exists a need for a simple, inexpensive field device for accurately measuring the thickness of insulating glass, particularly when an edge thereof is not available.